1. Field of the Invention
The present invention relates to an apparatus and a method for the coating treatment in which a substrate such as a semiconductor wafer is coated with a resist solution, followed by subjecting the resist coating to a heat treatment.
2. Description of the Related Art
In the photolithography step included in, for example, the manufacturing process of a semiconductor device, a semiconductor wafer is coated with a resist, followed by exposing the formed resist film to light in a predetermined circuit pattern. Then, the light-exposed circuit pattern is subjected to a developing treatment so as to form a circuit pattern in the resist film.
In general, various heat treatments are performed in the photolithography step including, for example, the heat treatment after the resist coating step (pre-bake), the heat treatment after the light exposure step (post exposure bake), and the heat treatment after the developing step (post bake). In general, such a heat treatment of the resist is performed by using a hot plate unit including a casing and a heating plate (hot plate) heated by a heater and arranged within the casing.
In the pre-bake treatment, various solvents contained in the resist solution are evaporated so as to form a resist film. Various kinds of solvents are contained in the resist depending on the kind of the resist, and the solvents used include, for example, those having a low boiling point and a high vapor pressure and those having a high boiling point and a low vapor pressure. These solvent components were discharged to the outside in the past in the form of a vapor contained in the hot exhaust gas from the hot plate unit. For example, the hot exhaust gas containing the vapor of such a solvent was transferred to a processing apparatus equipped with, for example, scrubbers through, for example, the piping of the plant in which was arranged the coating apparatus equipped with the hot plate unit, and the solvent component was removed in the processing apparatus.
One of the reasons for employing the particular method is that, since the solvent component contained in the conventional resist has a low boiling point and a high vapor pressure in many cases, the solvent vapor is scarcely cooled and condensed into a liquid and, thus, the piping is less contaminated, even if the hot exhaust gas is circulated through the piping of the plant.
However, with the rapid progress in recent years in the degree of integration and performance of the semiconductor devices, various components meeting the object of the use and various solvents for dissolving these components have come to be used in respect of the resist used for forming the circuit pattern.
For example, NMP (normal methyl pyrrolidone) having a high boiling point and a low vapor pressure is used as a component of polyimide series resist. Such a component having a high boiling point does not form a dew while the hot exhaust gas discharged from the hot plate unit has a high temperature. However, if the component is naturally cooled during flow within the piping so as to lower the temperature of component to a level close to room temperature, the component forms a dew within the piping so as to clog the piping, leading to the problem that the exhaust function of the piping is lowered. The clogging brings about the problem that the maintenance cost of the plant piping is increased.
An object of the present invention is to provide an apparatus and a method for the coating treatment, which prevent the solvent component of the hot exhaust gas discharged from the heating device from being condensed within the piping to form a dew.
According to a first aspect of the present invention, there is provided an apparatus for the coating treatment, in which a substrate is coated with a predetermined process solution, followed by applying a heat treatment to the resultant coating, comprising a coating section for coating the substrate with a process solution; a heating section for heating the substrate coated with said process solution; and a recovery section for recovering at least a part of the solvent vapor contained in the hot exhaust gas discharged from said heating section, wherein said recovery section includes a cooling apparatus for cooling and liquefying said solvent vapor for recovery of the liquefied solvent.
According to a second aspect of the present invention, there is provided a method for the coating treatment, in which a substrate having the surface coated with a predetermined process solution is arranged within a heating device for subjecting said substrate to a heat treatment within the heating device, comprising passing a hot exhaust gas containing a solvent vapor, which is generated from said process solution on the substrate when the substrate is arranged within said heating device, through a cooling apparatus such that at least a part of the solvent vapor contained in said exhaust gas is recovered as a liquid.
In the present invention, the hot exhaust gas discharged from the heating section (heating device) is cooled to a predetermined temperature so as to liquefy and remove the solvent vapor contained in the hot exhaust gas and, then, supplied to the piping of the plant, making it possible to suppress the dew formation within the piping of the plant. As a result, it is possible to carry out the heat treatment without lowering the exhaust function. It is also possible to lower the load required for the maintenance of the piping or the like of the plant. Further, the corrosion of the piping or the like of the plant caused by the solvent vapor or the like can be suppressed so as to prolong the life of the piping or the like of the plant. It is possible to control the removal rate of the solvent vapor by defining appropriately the construction, the scale, the cooling temperature, the hot exhaust gas flow rate, etc. of the cooling apparatus. In addition, the recovered solvent can be utilized again as a raw material. What should also be noted is that, if the cooling apparatus used is constructed to circulate at room temperature the cheap city water without using, for example, a chiller, the cost reduction can be achieved in respect of both the apparatus cost and the running cost.